Issue

Practical Electronics 101

03/01/2007

This issue of Advanced Packaging stands out for me because I had a chance to get to know more about practical issues that revolve around sockets. Modeling tinker toys in chemistry class and comparative anatomy classes taught me that, if you can take something apart and separate it into its most elemental parts, you can better understand how it works as a whole unit.

I distributed a questionnaire to those who buy, build, and use sockets that was broad, yet timely, and asked respondents to answer only the questions that they felt qualified to answer. And the answers that ensued became a two-part feature: the cover story of this issue, and Part II in the upcoming May/June issue.

Sockets are just plain interesting. For one thing, they’re useful in both final assemblies and testing applications. They allow the end user to swap out the packaged part in question, and insert a replacement or upgraded part. This type of activity is common in computer motherboards.

I asked my brother, Mark, to comment on the unfinished article, and I could tell that he was pleased. “I actually have had limited hands-on experience with those products,” he wrote. “I haven’t built a computer in a while; however, I think my last had a socket 7 for the CPU. I do see the need for standardization to make life easier for everyone.” This turned out to be the longest letter Mark ever wrote.

One engineer gave me the basic description of what happens during test, and that alone was educational. Almost all packaged parts go through a flow that requires them to be inserted into a socket, he said. The socket is used in tandem with a PCB to allow a test system to mate up with the packaged part. Each time a different-sized packaged part needs testing, a different size mating socket is required. This also requires adjustment in the PCB.

Avoiding waste is a good thing, so I asked what percent of ICs are thrown out for failing burn-in. The answer was not what I expected. Though it depends on the maturity of the specific packaged part, the complexity of the internal IC die, and the test itself, most users strive for fewer than 10% failure. In some cases, failure rate is so low that the manufacturing company may chose to remove this step if the customer agrees to accept the impact of not having a burn-in step. Surprised? I was.

When I asked which industries use the most sockets, most respondents didn’t even attempt to guess. One wrote that in final applications, almost every desktop or server computer has a socket in it to allow the user to swap out and replace the processor for numerous reasons. Therefore, it’s safe to say that more than 75 million ship each year in with sockets in them. As China, India, and other developing nations increase their demand for computers, this number will only rise.

I also learned how helpful these engineers are, and how capably they can teach others. One became so enthusiastic that he designed a collage of sockets which will appear in Part II of this feature. I am so thankful for the help of everyone who responded.